1. Field of the Invention
The present invention relates to musical tone generating apparatus and method that read out musical tone waveform data sampled and stored in a waveform memory and generate musical tones based on the musical tone waveform data, and a program for implementing the method.
2. Description of the Related Art
Conventionally, a so-called waveform table (wave table) tone generator is known which stores waveform data prepared by sampling tones of a musical instrument in a waveform memory, and generates musical tones by reading out the waveform data from the waveform memory.
In the above conventional waveform table tone generator, to reduce the storage capacity of the waveform memory, musical tones are sometimes sampled at a lower frequency than the original sampling frequency of the tone generator system, specifically, a frequency at which musical tones are generated by reading out musical tone waveform data from the waveform memory. Hereinafter, the original sampling frequency of the tone generator system will be referred to as “the sampling frequency”, and the frequency at which musical tones are sampled to generate musical tone waveform data will be referred to as “the recording sampling frequency”. It should be noted that the term “recording sampling frequency” is intended to mean not only the sampling frequency at which musical tones are directly recorded or sampled but also a sampling frequency at which the musical tones once sampled are re-sampled (down-sampled).
The recording sampling frequency corresponds to the number of musical tone waveform samples (waveform samples forming musical tone waveform data) per unit time (one second), and hence, as the recording sampling frequency is lowered, the volume of the stored musical tone waveform data is reduced. This reduces the capacity of the waveform memory necessary for the storage of the musical tone waveform data.
However, according to the sampling theorem, the recording sampling frequency determines the upper limit frequency (=half the recording sampling frequency) of reproducible musical tones (assuming that the recording sampling frequency is 16 KHz, musical tones whose frequency range is up to 8 KHz can be reproduced). In other words, when the recording sampling frequency is held low, musical tones missing high-order harmonic components thereof are reproduced, which results in degraded quality of the reproduced musical tones.